I. Field of the Invention
This invention relates to expansible retaining clamps provided with spring loading for clasping objects disposed therebetween. The invention is applicable to use for bookends and as well for use as a shop clamp for plywood or other stackable materials, for the storage and retention of objects such as records, computer diskettes, video tapes, and similar usages where their is a requirement for storing objects vertically for later use.
II. Description of the Prior Art
A number of spring loaded bookracks or clamping means are shown in the prior art. Examples of these prior art patents are that to Walker, U.S. Pat. No. 153,227, in which a spring is arranged in the base of the bookrack drawing a pair of ways against books held between the ways. Opposite ends of the spring in the Walker device draw the ways against the books in the form of a main spring.
Another illustration of a spring loaded bookend is the patent to Schreyer, U.S. Pat. No. 2,284,849, in which a pair of complementally shaped bookends are provided, one of the bookends being provided with an elongated spring disposed laterally through one of the bookends and attached at an opposite extremity to the opposite complemental bookend. In use, a book is slipped between the two bookends and they automatically separate by expansion of the spring the requisite amount in linear travel.
A further variation on a bookend is that in the Clift U.S. Pat. No. 2,334,251, in which a pair of bookends are provided with a slot through which passes a cord, opposite ends of which are used to grasp a figure having a lug to which the cord may be attached on each bookend. The adjustment here entails winding or unwinding a number of turns of the cord on the lug or placement of it on a different lug so as to increase or decrease the expansion.
Still another variation is the patent to Bascom, U.S. Pat. No. 3,399,782, in which a pair of bookends are connected together by means of a length of elastic which expands or retracts over rollers in the walls of the bookends to take up or play out the elastic and allow for variation and separation of the bookends.
A further variation is the patent to Cawood, U.S. Pat. No. 4,135,626, which discloses a holding device to apply a constant force on objects held between complementally formed retaining clamps. A constant force spring is coiled at opposite ends of the pair of clamps and is used to draw the two objects together to hold materials therebetween or allow expansion of the bookends.